<?php
// +----------------------------------------------------------------------
// | ThinkPHP [ WE CAN DO IT JUST THINK IT ]
// +----------------------------------------------------------------------
// | Copyright (c) 2006-2012 http://thinkphp.cn All rights reserved.
// +----------------------------------------------------------------------
// | Licensed ( http://www.apache.org/licenses/LICENSE-2.0 )
// +----------------------------------------------------------------------
// | Author: liu21st <liu21st@gmail.com>
// +----------------------------------------------------------------------

/**
 * ThinkPHP 数据库中间层实现类
 * @category   Think
 * @package  Think
 * @subpackage  Core
 * @author    liu21st <liu21st@gmail.com>
 */
class Db {
	// 数据库类型
	protected $dbType     = null;
	// 是否自动释放查询结果
	protected $autoFree   = false;
	// 当前操作所属的模型名
	protected $model      = '_think_';
	// 是否使用永久连接
	protected $pconnect   = false;
	// 当前SQL指令
	protected $queryStr   = '';
	protected $modelSql   = array();
	// 最后插入ID
	protected $lastInsID  = null;
	// 返回或者影响记录数
	protected $numRows    = 0;
	// 返回字段数
	protected $numCols    = 0;
	// 事务指令数
	protected $transTimes = 0;
	// 错误信息
	protected $error      = '';
	// 数据库连接ID 支持多个连接
	protected $linkID     = array();
	// 当前连接ID
	protected $_linkID    = null;
	// 当前查询ID
	protected $queryID    = null;
	// 是否已经连接数据库
	protected $connected  = false;
	// 数据库连接参数配置
	protected $config     = '';
	// 数据库表达式
	protected $comparison = array('eq'=>'=','neq'=>'<>','gt'=>'>','egt'=>'>=','lt'=>'<','elt'=>'<=','notlike'=>'NOT LIKE','like'=>'LIKE','in'=>'IN','notin'=>'NOT IN');
	// 查询表达式
	protected $selectSql  = 'SELECT%DISTINCT% %FIELD% FROM %TABLE%%JOIN%%WHERE%%GROUP%%HAVING%%ORDER%%LIMIT% %UNION%%COMMENT%';

	/**
	 * 取得数据库类实例
	 * @static
	 * @access public
	 * @return mixed 返回数据库驱动类
	 */
	public static function getInstance() {
		$args = func_get_args();
		return get_instance_of(__CLASS__,'factory',$args);
	}

	/**
	 * 加载数据库 支持配置文件或者 DSN
	 * @access public
	 * @param mixed $db_config 数据库配置信息
	 * @return string
	 */
	public function factory($db_config='') {
		// 读取数据库配置
		$db_config = $this->parseConfig($db_config);
		if(empty($db_config['dbms']))
		throw_exception(L('_NO_DB_CONFIG_'));
		// 数据库类型
		$this->dbType = ucwords(strtolower($db_config['dbms']));
		$class = 'Db'. $this->dbType;
		// 检查驱动类
		if(class_exists($class)) {
			$db = new $class($db_config);
			// 获取当前的数据库类型
			if( 'pdo' != strtolower($db_config['dbms']) )
			$db->dbType = strtoupper($this->dbType);
			else
			$db->dbType = $this->_getDsnType($db_config['dsn']);
		}else {
			// 类没有定义
			throw_exception(L('_NO_DB_DRIVER_').': ' . $class);
		}
		return $db;
	}

	/**
	 * 根据DSN获取数据库类型 返回大写
	 * @access protected
	 * @param string $dsn  dsn字符串
	 * @return string
	 */
	protected function _getDsnType($dsn) {
		$match  =  explode(':',$dsn);
		$dbType = strtoupper(trim($match[0]));
		return $dbType;
	}

	/**
	 * 分析数据库配置信息，支持数组和DSN
	 * @access private
	 * @param mixed $db_config 数据库配置信息
	 * @return string
	 */
	private function parseConfig($db_config='') {
		if ( !empty($db_config) && is_string($db_config)) {
			// 如果DSN字符串则进行解析
			$db_config = $this->parseDSN($db_config);
		}elseif(is_array($db_config)) { // 数组配置
			$db_config =   array_change_key_case($db_config);
			$db_config = array(
                  'dbms'      =>  $db_config['db_type'],
                  'username'  =>  $db_config['db_user'],
                  'password'  =>  $db_config['db_pwd'],
                  'hostname'  =>  $db_config['db_host'],
                  'hostport'  =>  $db_config['db_port'],
                  'database'  =>  $db_config['db_name'],
                  'dsn'       =>  $db_config['db_dsn'],
                  'params'    =>  $db_config['db_params'],
			);
		}elseif(empty($db_config)) {
			// 如果配置为空，读取配置文件设置
			if( C('DB_DSN') && 'pdo' != strtolower(C('DB_TYPE')) ) { // 如果设置了DB_DSN 则优先
				$db_config =  $this->parseDSN(C('DB_DSN'));
			}else{
				$db_config = array (
                    'dbms'      =>  C('DB_TYPE'),
                    'username'  =>  C('DB_USER'),
                    'password'  =>  C('DB_PWD'),
                    'hostname'  =>  C('DB_HOST'),
                    'hostport'  =>  C('DB_PORT'),
                    'database'  =>  C('DB_NAME'),
                    'dsn'       =>  C('DB_DSN'),
                    'params'    =>  C('DB_PARAMS'),
				);
			}
		}
		return $db_config;
	}

	/**
	 * 初始化数据库连接
	 * @access protected
	 * @param boolean $master 主服务器
	 * @return void
	 */
	protected function initConnect($master=true) {
		if(1 == C('DB_DEPLOY_TYPE'))
		// 采用分布式数据库
		$this->_linkID = $this->multiConnect($master);
		else
		// 默认单数据库
		if ( !$this->connected ) $this->_linkID = $this->connect();
	}

	/**
	 * 连接分布式服务器
	 * @access protected
	 * @param boolean $master 主服务器
	 * @return void
	 */
	protected function multiConnect($master=false) {
		static $_config = array();
		if(empty($_config)) {
			// 缓存分布式数据库配置解析
			foreach ($this->config as $key=>$val){
				$_config[$key]      =   explode(',',$val);
			}
		}
		// 数据库读写是否分离
		if(C('DB_RW_SEPARATE')){
			// 主从式采用读写分离
			if($master)
			// 主服务器写入
			$r  =   floor(mt_rand(0,C('DB_MASTER_NUM')-1));
			else{
				if(is_numeric(C('DB_SLAVE_NO'))) {// 指定服务器读
					$r = C('DB_SLAVE_NO');
				}else{
					// 读操作连接从服务器
					$r = floor(mt_rand(C('DB_MASTER_NUM'),count($_config['hostname'])-1));   // 每次随机连接的数据库
				}
			}
		}else{
			// 读写操作不区分服务器
			$r = floor(mt_rand(0,count($_config['hostname'])-1));   // 每次随机连接的数据库
		}
		$db_config = array(
            'username'  =>  isset($_config['username'][$r])?$_config['username'][$r]:$_config['username'][0],
            'password'  =>  isset($_config['password'][$r])?$_config['password'][$r]:$_config['password'][0],
            'hostname'  =>  isset($_config['hostname'][$r])?$_config['hostname'][$r]:$_config['hostname'][0],
            'hostport'  =>  isset($_config['hostport'][$r])?$_config['hostport'][$r]:$_config['hostport'][0],
            'database'  =>  isset($_config['database'][$r])?$_config['database'][$r]:$_config['database'][0],
            'dsn'       =>  isset($_config['dsn'][$r])?$_config['dsn'][$r]:$_config['dsn'][0],
            'params'    =>  isset($_config['params'][$r])?$_config['params'][$r]:$_config['params'][0],
		);
		return $this->connect($db_config,$r);
	}

	/**
	 * DSN解析
	 * 格式： mysql://username:passwd@localhost:3306/DbName
	 * @static
	 * @access public
	 * @param string $dsnStr
	 * @return array
	 */
	public function parseDSN($dsnStr) {
		if( empty($dsnStr) ){return false;}
		$info = parse_url($dsnStr);
		if($info['scheme']){
			$dsn = array(
            'dbms'      =>  $info['scheme'],
            'username'  =>  isset($info['user']) ? $info['user'] : '',
            'password'  =>  isset($info['pass']) ? $info['pass'] : '',
            'hostname'  =>  isset($info['host']) ? $info['host'] : '',
            'hostport'  =>  isset($info['port']) ? $info['port'] : '',
            'database'  =>  isset($info['path']) ? substr($info['path'],1) : ''
            );
		}else {
			preg_match('/^(.*?)\:\/\/(.*?)\:(.*?)\@(.*?)\:([0-9]{1, 6})\/(.*?)$/',trim($dsnStr),$matches);
			$dsn = array (
            'dbms'      =>  $matches[1],
            'username'  =>  $matches[2],
            'password'  =>  $matches[3],
            'hostname'  =>  $matches[4],
            'hostport'  =>  $matches[5],
            'database'  =>  $matches[6]
			);
		}
		$dsn['dsn'] =  ''; // 兼容配置信息数组
		return $dsn;
	}

	/**
	 * 数据库调试 记录当前SQL
	 * @access protected
	 */
	protected function debug() {
		$this->modelSql[$this->model]   =  $this->queryStr;
		$this->model  =   '_think_';
		// 记录操作结束时间
		if (C('DB_SQL_LOG')) {
			G('queryEndTime');
			trace($this->queryStr.' [ RunTime:'.G('queryStartTime','queryEndTime',6).'s ]','','SQL');
		}
	}

	/**
	 * 设置锁机制
	 * @access protected
	 * @return string
	 */
	protected function parseLock($lock=false) {
		if(!$lock) return '';
		if('ORACLE' == $this->dbType) {
			return ' FOR UPDATE NOWAIT ';
		}
		return ' FOR UPDATE ';
	}

	/**
	 * set分析
	 * @access protected
	 * @param array $data
	 * @return string
	 */
	protected function parseSet($data) {
		foreach ($data as $key=>$val){
			$value   =  $this->parseValue($val);
			if(is_scalar($value)) // 过滤非标量数据
			$set[]    = $this->parseKey($key).'='.$value;
		}
		return ' SET '.implode(',',$set);
	}

	/**
	 * 字段名分析
	 * @access protected
	 * @param string $key
	 * @return string
	 */
	protected function parseKey(&$key) {
		return $key;
	}

	/**
	 * value分析
	 * @access protected
	 * @param mixed $value
	 * @return string
	 */
	protected function parseValue($value) {
		if(is_string($value)) {
			$value =  '\''.$this->escapeString($value).'\'';
		}elseif(isset($value[0]) && is_string($value[0]) && strtolower($value[0]) == 'exp'){
			$value =  $this->escapeString($value[1]);
		}elseif(is_array($value)) {
			$value =  array_map(array($this, 'parseValue'),$value);
		}elseif(is_bool($value)){
			$value =  $value ? '1' : '0';
		}elseif(is_null($value)){
			$value =  'null';
		}
		return $value;
	}

	/**
	 * field分析
	 * @access protected
	 * @param mixed $fields
	 * @return string
	 */
	protected function parseField($fields) {
		if(is_string($fields) && strpos($fields,',')) {
			$fields    = explode(',',$fields);
		}
		if(is_array($fields)) {
			// 完善数组方式传字段名的支持
			// 支持 'field1'=>'field2' 这样的字段别名定义
			$array   =  array();
			foreach ($fields as $key=>$field){
				if(!is_numeric($key))
				$array[] =  $this->parseKey($key).' AS '.$this->parseKey($field);
				else
				$array[] =  $this->parseKey($field);
			}
			$fieldsStr = implode(',', $array);
		}elseif(is_string($fields) && !empty($fields)) {
			$fieldsStr = $this->parseKey($fields);
		}else{
			$fieldsStr = '*';
		}
		//TODO 如果是查询全部字段，并且是join的方式，那么就把要查的表加个别名，以免字段被覆盖
		return $fieldsStr;
	}

	/**
	 * table分析
	 * @access protected
	 * @param mixed $table
	 * @return string
	 */
	protected function parseTable($tables) {
		if(is_array($tables)) {// 支持别名定义
			$array   =  array();
			foreach ($tables as $table=>$alias){
				if(!is_numeric($table))
				$array[] =  $this->parseKey($table).' '.$this->parseKey($alias);
				else
				$array[] =  $this->parseKey($table);
			}
			$tables  =  $array;
		}elseif(is_string($tables)){
			$tables  =  explode(',',$tables);
			array_walk($tables, array(&$this, 'parseKey'));
		}
		return implode(',',$tables);
	}

	/**
	 * where分析
	 * @access protected
	 * @param mixed $where
	 * @return string
	 */
	protected function parseWhere($where) {
		$whereStr = '';
		if(is_string($where)) {
			// 直接使用字符串条件
			$whereStr = $where;
		}else{ // 使用数组表达式
			$operate  = isset($where['_logic'])?strtoupper($where['_logic']):'';
			if(in_array($operate,array('AND','OR','XOR'))){
				// 定义逻辑运算规则 例如 OR XOR AND NOT
				$operate    =   ' '.$operate.' ';
				unset($where['_logic']);
			}else{
				// 默认进行 AND 运算
				$operate    =   ' AND ';
			}
			foreach ($where as $key=>$val){
				$whereStr .= '( ';
				if(0===strpos($key,'_')) {
					// 解析特殊条件表达式
					$whereStr   .= $this->parseThinkWhere($key,$val);
				}else{
					// 查询字段的安全过滤
					if(!preg_match('/^[A-Z_\|\&\-.a-z0-9\(\)\,]+$/',trim($key))){
						throw_exception(L('_EXPRESS_ERROR_').':'.$key);
					}
					// 多条件支持
					$multi  = is_array($val) &&  isset($val['_multi']);
					$key    = trim($key);
					if(strpos($key,'|')) { // 支持 name|title|nickname 方式定义查询字段
						$array =  explode('|',$key);
						$str   =  array();
						foreach ($array as $m=>$k){
							$v =  $multi?$val[$m]:$val;
							$str[]   = '('.$this->parseWhereItem($this->parseKey($k),$v).')';
						}
						$whereStr .= implode(' OR ',$str);
					}elseif(strpos($key,'&')){
						$array =  explode('&',$key);
						$str   =  array();
						foreach ($array as $m=>$k){
							$v =  $multi?$val[$m]:$val;
							$str[]   = '('.$this->parseWhereItem($this->parseKey($k),$v).')';
						}
						$whereStr .= implode(' AND ',$str);
					}else{
						$whereStr .= $this->parseWhereItem($this->parseKey($key),$val);
					}
				}
				$whereStr .= ' )'.$operate;
			}
			$whereStr = substr($whereStr,0,-strlen($operate));
		}
		return empty($whereStr)?'':' WHERE '.$whereStr;
	}

	// where子单元分析
	protected function parseWhereItem($key,$val) {
		$whereStr = '';
		if(is_array($val)) {
			if(is_string($val[0])) {
				if(preg_match('/^(EQ|NEQ|GT|EGT|LT|ELT)$/i',$val[0])) { // 比较运算
					$whereStr .= $key.' '.$this->comparison[strtolower($val[0])].' '.$this->parseValue($val[1]);
				}elseif(preg_match('/^(NOTLIKE|LIKE)$/i',$val[0])){// 模糊查找
					if(is_array($val[1])) {
						$likeLogic  =   isset($val[2])?strtoupper($val[2]):'OR';
						if(in_array($likeLogic,array('AND','OR','XOR'))){
							$likeStr    =   $this->comparison[strtolower($val[0])];
							$like       =   array();
							foreach ($val[1] as $item){
								$like[] = $key.' '.$likeStr.' '.$this->parseValue($item);
							}
							$whereStr .= '('.implode(' '.$likeLogic.' ',$like).')';
						}
					}else{
						$whereStr .= $key.' '.$this->comparison[strtolower($val[0])].' '.$this->parseValue($val[1]);
					}
				}elseif('exp'==strtolower($val[0])){ // 使用表达式
					$whereStr .= ' ('.$key.' '.$val[1].') ';
				}elseif(preg_match('/IN/i',$val[0])){ // IN 运算
					if(isset($val[2]) && 'exp'==$val[2]) {
						$whereStr .= $key.' '.strtoupper($val[0]).' '.$val[1];
					}else{
						if(is_string($val[1])) {
							$val[1] =  explode(',',$val[1]);
						}
						$zone      =   implode(',',$this->parseValue($val[1]));
						$whereStr .= $key.' '.strtoupper($val[0]).' ('.$zone.')';
					}
				}elseif(preg_match('/BETWEEN/i',$val[0])){ // BETWEEN运算
					$data = is_string($val[1])? explode(',',$val[1]):$val[1];
					$whereStr .=  ' ('.$key.' '.strtoupper($val[0]).' '.$this->parseValue($data[0]).' AND '.$this->parseValue($data[1]).' )';
				}else{
					throw_exception(L('_EXPRESS_ERROR_').':'.$val[0]);
				}
			}else {
				$count = count($val);
				$rule  = isset($val[$count-1])?strtoupper($val[$count-1]):'';
				if(in_array($rule,array('AND','OR','XOR'))) {
					$count  = $count -1;
				}else{
					$rule   = 'AND';
				}
				for($i=0;$i<$count;$i++) {
					$data = is_array($val[$i])?$val[$i][1]:$val[$i];
					if('exp'==strtolower($val[$i][0])) {
						$whereStr .= '('.$key.' '.$data.') '.$rule.' ';
					}else{
						$op = is_array($val[$i])?$this->comparison[strtolower($val[$i][0])]:'=';
						$whereStr .= '('.$key.' '.$op.' '.$this->parseValue($data).') '.$rule.' ';
					}
				}
				$whereStr = substr($whereStr,0,-4);
			}
		}else {
			//对字符串类型字段采用模糊匹配
			if(C('DB_LIKE_FIELDS') && preg_match('/('.C('DB_LIKE_FIELDS').')/i',$key)) {
				$val  =  '%'.$val.'%';
				$whereStr .= $key.' LIKE '.$this->parseValue($val);
			}else {
				$whereStr .= $key.' = '.$this->parseValue($val);
			}
		}
		return $whereStr;
	}

	/**
	 * 特殊条件分析
	 * @access protected
	 * @param string $key
	 * @param mixed $val
	 * @return string
	 */
	protected function parseThinkWhere($key,$val) {
		$whereStr   = '';
		switch($key) {
			case '_string':
				// 字符串模式查询条件
				$whereStr = $val;
				break;
			case '_complex':
				// 复合查询条件
				$whereStr = substr($this->parseWhere($val),6);
				break;
			case '_query':
				// 字符串模式查询条件
				parse_str($val,$where);
				if(isset($where['_logic'])) {
					$op   =  ' '.strtoupper($where['_logic']).' ';
					unset($where['_logic']);
				}else{
					$op   =  ' AND ';
				}
				$array   =  array();
				foreach ($where as $field=>$data)
				$array[] = $this->parseKey($field).' = '.$this->parseValue($data);
				$whereStr   = implode($op,$array);
				break;
		}
		return $whereStr;
	}

	/**
	 * limit分析
	 * @access protected
	 * @param mixed $lmit
	 * @return string
	 */
	protected function parseLimit($limit) {
		return !empty($limit)?   ' LIMIT '.$limit.' ':'';
	}

	/**
	 * join分析
	 * @access protected
	 * @param mixed $join
	 * @return string
	 */
	protected function parseJoin($join) {
		$joinStr = '';
		if(!empty($join)) {
			if(is_array($join)) {
				foreach ($join as $key=>$_join){
					if(false !== stripos($_join,'JOIN'))
					$joinStr .= ' '.$_join;
					else
					$joinStr .= ' LEFT JOIN ' .$_join;
				}
			}else{
				$joinStr .= ' LEFT JOIN ' .$join;
			}
		}
		//将__TABLE_NAME__这样的字符串替换成正规的表名,并且带上前缀和后缀
		$joinStr = preg_replace("/__([A-Z_-]+)__/esU",C("DB_PREFIX").".strtolower('$1')",$joinStr);
		return $joinStr;
	}

	/**
	 * order分析
	 * @access protected
	 * @param mixed $order
	 * @return string
	 */
	protected function parseOrder($order) {
		if(is_array($order)) {
			$array   =  array();
			foreach ($order as $key=>$val){
				if(is_numeric($key)) {
					$array[] =  $this->parseKey($val);
				}else{
					$array[] =  $this->parseKey($key).' '.$val;
				}
			}
			$order   =  implode(',',$array);
		}
		return !empty($order)?  ' ORDER BY '.$order:'';
	}

	/**
	 * group分析
	 * @access protected
	 * @param mixed $group
	 * @return string
	 */
	protected function parseGroup($group) {
		return !empty($group)? ' GROUP BY '.$group:'';
	}

	/**
	 * having分析
	 * @access protected
	 * @param string $having
	 * @return string
	 */
	protected function parseHaving($having) {
		return  !empty($having)?   ' HAVING '.$having:'';
	}

	/**
	 * comment分析
	 * @access protected
	 * @param string $comment
	 * @return string
	 */
	protected function parseComment($comment) {
		return  !empty($comment)?   ' /* '.$comment.' */':'';
	}

	/**
	 * distinct分析
	 * @access protected
	 * @param mixed $distinct
	 * @return string
	 */
	protected function parseDistinct($distinct) {
		return !empty($distinct)?   ' DISTINCT ' :'';
	}

	/**
	 * union分析
	 * @access protected
	 * @param mixed $union
	 * @return string
	 */
	protected function parseUnion($union) {
		if(empty($union)) return '';
		if(isset($union['_all'])) {
			$str  =   'UNION ALL ';
			unset($union['_all']);
		}else{
			$str  =   'UNION ';
		}
		foreach ($union as $u){
			$sql[] = $str.(is_array($u)?$this->buildSelectSql($u):$u);
		}
		return implode(' ',$sql);
	}

	/**
	 * 插入记录
	 * @access public
	 * @param mixed $data 数据
	 * @param array $options 参数表达式
	 * @param boolean $replace 是否replace
	 * @return false | integer
	 */
	public function insert($data,$options=array(),$replace=false) {
		$values  =  $fields    = array();
		$this->model  =   $options['model'];
		foreach ($data as $key=>$val){
			$value   =  $this->parseValue($val);
			if(is_scalar($value)) { // 过滤非标量数据
				$values[]   =  $value;
				$fields[]   =  $this->parseKey($key);
			}
		}
		$sql   =  ($replace?'REPLACE':'INSERT').' INTO '.$this->parseTable($options['table']).' ('.implode(',', $fields).') VALUES ('.implode(',', $values).')';
		$sql   .= $this->parseLock(isset($options['lock'])?$options['lock']:false);
		$sql   .= $this->parseComment(!empty($options['comment'])?$options['comment']:'');
		return $this->execute($sql);
	}

	/**
	 * 通过Select方式插入记录
	 * @access public
	 * @param string $fields 要插入的数据表字段名
	 * @param string $table 要插入的数据表名
	 * @param array $option  查询数据参数
	 * @return false | integer
	 */
	public function selectInsert($fields,$table,$options=array()) {
		$this->model  =   $options['model'];
		if(is_string($fields))   $fields    = explode(',',$fields);
		array_walk($fields, array($this, 'parseKey'));
		$sql   =    'INSERT INTO '.$this->parseTable($table).' ('.implode(',', $fields).') ';
		$sql   .= $this->buildSelectSql($options);
		return $this->execute($sql);
	}

	/**
	 * 更新记录
	 * @access public
	 * @param mixed $data 数据
	 * @param array $options 表达式
	 * @return false | integer
	 */
	public function update($data,$options) {
		$this->model  =   $options['model'];
		$sql   = 'UPDATE '
		.$this->parseTable($options['table'])
		.$this->parseSet($data)
		.$this->parseWhere(!empty($options['where'])?$options['where']:'')
		.$this->parseOrder(!empty($options['order'])?$options['order']:'')
		.$this->parseLimit(!empty($options['limit'])?$options['limit']:'')
		.$this->parseLock(isset($options['lock'])?$options['lock']:false)
		.$this->parseComment(!empty($options['comment'])?$options['comment']:'');
		return $this->execute($sql);
	}

	/**
	 * 删除记录
	 * @access public
	 * @param array $options 表达式
	 * @return false | integer
	 */
	public function delete($options=array()) {
		$this->model  =   $options['model'];
		$sql   = 'DELETE FROM '
		.$this->parseTable($options['table'])
		.$this->parseWhere(!empty($options['where'])?$options['where']:'')
		.$this->parseOrder(!empty($options['order'])?$options['order']:'')
		.$this->parseLimit(!empty($options['limit'])?$options['limit']:'')
		.$this->parseLock(isset($options['lock'])?$options['lock']:false)
		.$this->parseComment(!empty($options['comment'])?$options['comment']:'');
		return $this->execute($sql);
	}

	/**
	 * 查找记录
	 * @access public
	 * @param array $options 表达式
	 * @return mixed
	 */
	public function select($options=array()) {
		$this->model  =   $options['model'];
		$sql    = $this->buildSelectSql($options);
		$cache  =  isset($options['cache'])?$options['cache']:false;
		if($cache) { // 查询缓存检测
			$key    =  is_string($cache['key'])?$cache['key']:md5($sql);
			$value  =  S($key,'',$cache);
			if(false !== $value) {
				return $value;
			}
		}
		$result   = $this->query($sql);
		if($cache && false !== $result ) { // 查询缓存写入
			S($key,$result,$cache);
		}
		return $result;
	}

	/**
	 * 生成查询SQL
	 * @access public
	 * @param array $options 表达式
	 * @return string
	 */
	public function buildSelectSql($options=array()) {
		if(isset($options['page'])) {
			// 根据页数计算limit
			if(strpos($options['page'],',')) {
				list($page,$listRows) =  explode(',',$options['page']);
			}else{
				$page = $options['page'];
			}
			$page    =  $page?$page:1;
			$listRows=  isset($listRows)?$listRows:(is_numeric($options['limit'])?$options['limit']:20);
			$offset  =  $listRows*((int)$page-1);
			$options['limit'] =  $offset.','.$listRows;
		}
		if(C('DB_SQL_BUILD_CACHE')) { // SQL创建缓存
			$key    =  md5(serialize($options));
			$value  =  S($key);
			if(false !== $value) {
				return $value;
			}
		}
		$sql  =   $this->parseSql($this->selectSql,$options);
		$sql .= $this->parseLock(isset($options['lock'])?$options['lock']:false);
		if(isset($key)) { // 写入SQL创建缓存
			S($key,$sql,array('expire'=>0,'length'=>C('DB_SQL_BUILD_LENGTH'),'queue'=>C('DB_SQL_BUILD_QUEUE')));
		}
		return $sql;
	}

	/**
	 * 替换SQL语句中表达式
	 * @access public
	 * @param array $options 表达式
	 * @return string
	 */
	public function parseSql($sql,$options=array()){
		$sql   = str_replace(
		array('%TABLE%','%DISTINCT%','%FIELD%','%JOIN%','%WHERE%','%GROUP%','%HAVING%','%ORDER%','%LIMIT%','%UNION%','%COMMENT%'),
		array(
		$this->parseTable($options['table']),
		$this->parseDistinct(isset($options['distinct'])?$options['distinct']:false),
		$this->parseField(!empty($options['field'])?$options['field']:'*'),
		$this->parseJoin(!empty($options['join'])?$options['join']:''),
		$this->parseWhere(!empty($options['where'])?$options['where']:''),
		$this->parseGroup(!empty($options['group'])?$options['group']:''),
		$this->parseHaving(!empty($options['having'])?$options['having']:''),
		$this->parseOrder(!empty($options['order'])?$options['order']:''),
		$this->parseLimit(!empty($options['limit'])?$options['limit']:''),
		$this->parseUnion(!empty($options['union'])?$options['union']:''),
		$this->parseComment(!empty($options['comment'])?$options['comment']:'')
		),$sql);
		return $sql;
	}

	/**
	 * 获取最近一次查询的sql语句
	 * @param string $model  模型名
	 * @access public
	 * @return string
	 */
	public function getLastSql($model='') {
		return $model?$this->modelSql[$model]:$this->queryStr;
	}

	/**
	 * 获取最近插入的ID
	 * @access public
	 * @return string
	 */
	public function getLastInsID() {
		return $this->lastInsID;
	}

	/**
	 * 获取最近的错误信息
	 * @access public
	 * @return string
	 */
	public function getError() {
		return $this->error;
	}

	/**
	 * SQL指令安全过滤
	 * @access public
	 * @param string $str  SQL字符串
	 * @return string
	 */
	public function escapeString($str) {
		return addslashes($str);
	}

	/**
	 * 设置当前操作模型
	 * @access public
	 * @param string $model  模型名
	 * @return void
	 */
	public function setModel($model){
		$this->model =  $model;
	}

	/**
	 * 析构方法
	 * @access public
	 */
	public function __destruct() {
		// 释放查询
		if ($this->queryID){
			$this->free();
		}
		// 关闭连接
		$this->close();
	}

	// 关闭数据库 由驱动类定义
	public function close(){}
}